Within your Request Manager you will see a 'My Licences' folder.
Any licences that have been granted will appear in this folder and you can download the invoice by clicking on the PDF icon:
Alternatively, you can download a copy of your licence document by clicking on the licensed request.
Within the Request Comments section, there will be a bubble indicating that the request has been licensed or paid for:
You should be able to click the link to download a PDF copy of the agreement.
Requests paid for by credit card will also contain a link to a credit card receipt.